Project Summary Each year, nearly 7,200 infants in the United States are born with a complex congenital heart disease that requires surgical intervention within the first year of life. For infants and young children with heart rhythm abnormalities, interventional treatment can be especially difficult, as the size of their vasculature and/or congenital anomalies typically preclude a transvenous approach for implanting a cardiac device such as a pacemaker or defibrillator. As a result, infants must undergo a sternotomy or thoracotomy to access the epicardial surface of the heart. We have developed a novel minimally-invasive pericardial access tool to deliver pacing and defibrillation leads to the epicardial surface of the heart under direct visualization from an endoscope. Utilizing this tool, we hypothesize that we can safely and effectively deliver pacing and defibrillation therapy through a single small port. By using a percutaneous approach, this should reduce pain and risk of infection, decrease procedure times, and minimize operative complications from an open surgical approach. In addition, direct visualization of the procedure makes it safer than blind pericardial punctures. Our team has utilized an immature porcine model for the acute implantation of cardiac devices. We also demonstrated that cardiac therapy delivered by percutaneous approach was as safe and effective as an open surgical technique. The specific, near-term goal of this project is to assess long-term safety and efficacy of the implantation tool and techniques through the following 2 specific aims: Aim 1: Improve the design and develop the process to manufacture the pericardial access tool for preclinical bench testing. Success is defined as producing a minimum of 30 units that pass preclinical bench testing, sterilization, and post production quality controls. Aim 2: Assess the safety of the pericardial access tool in an acute (Aim 2.1) comparison study to thoracic trocars, and the efficacy (Aim 2.2) of accessing the pericardial space in a pericardial adhesion model. Success is defined as demonstrating safety of the procedure in acute infant piglets, with functional pacemakers / defibrillators 2 months after implant in the efficacy study. This research could have a transformative impact in changing current clinical practice by converting an open surgical approach to a minimally invasive percutaneous procedure. While the study design focuses on the unique needs of infants and children with congenital heart disease, extrapolation of these findings may benefit thousands of adult patients who have indications for cardiac resynchronization therapy but do not achieve successful implantation due to lack of transvenous access or adequate coronary sinus venous tributaries to pace key locations in the left ventricle, which could be resolved with our proposed tools and techniques.